1. Field of the Invention
The invention relates to off-axis displays arranged for producing three-dimensional (3D) illusions that appear to project beyond surfaces of the displays and to methods of capturing, processing, and displaying images for 3D projection.
2. Description of Related Art
Three-dimensional (3D) imaging methods have been in use for many years. Among these, autostereoscopic 3D imaging systems, which do not require the use of visual aids such as cross-polarizing eyeglasses, have become increasing popular. For example, 3D holograms and lenticular displays are now commonplace.
Addressable displays capable of displaying multiple or even moving 3D images include both volumetric and parallax displays. Volumetric display systems collect three-dimensional image data throughout a volume of space and display the image data as a series of image slices through different depths of the volume. The resulting images are visible through a wide range of viewing angles but generally do not provide appropriate occlusion or shading for objects obscured by other objects as required for realistic viewing of scenes. The optical and mechanical technologies required for producing such images also tend to be quite expensive.
Parallax displays present directionally varying information so that slightly different images are presented to each of an observer's eyes. For example, parallax displays can present slightly offset images of the same scene to an observer's eyes mimicking the natural offset of the observer's eyes and exploiting the predispositions of the observer's mental processing of such offset views for acquiring three-dimensional information.
Generally, the known parallax displays present 3D images in standard viewing orientations for on-axis viewing. For example, the image display surface is typically placed in a vertical orientation normal to the line of sight of a typical standing or seated observer. Only limited depth is available receding into the background of a scene. In addition, known parallax displays have a limited capability for projecting dimensional perspective forward of the plane of the image display surface. These standard parallax methods have been in the marketplace and practiced in their current forms for approximately 100 years and as such do not provide a new and unique display opportunities for potential commercial users.
The creation of 2D and 3D images that are designed to have correct perspective when viewed from angles far from the normal to the image surface have long been known to the art. A 2D painting technique called anamorphosis, which is designed to produce this effect, dates back to the Renaissance. Objects are painted so that they appear to have correct perspective when viewed from far off to one side, instead of straight on as in a normal panting. In the modern era such paintings are sometimes created on sidewalks or public squares by artists and are rendered so a person walking toward them along a sidewalk will, at least for a moment, see a correctly proportioned image of an object or person sitting on the sidewalk in front of them. Trompe l'oeil artists employ the same techniques in public art created on vertical surfaces like walls and the faces of buildings.
Stereo 3D images that employ these techniques began to appear in the early 1900s. A drawing of a cylinder, designed for viewing with red and green glasses, was published in the book Les Anaglyphes Geometriques in 1912. An early U.S. Pat. No. 1,592,034 (Macy, 1926) describes a simplified variation of this technique applied to horizontally oriented stereo images. Later in the century several books were published that contained stereo anaglyph drawings and in some cases instructions on how to draw them. These books include Descriptive Geometry with Three Dimensional figures by Imre Pal (1959), Engineering Graphics and Descriptive Geometry in 3-D by G. F. Pearce (1977), Phantogram Perspective Charts by Raymond Nicyper (1979) and Stereo Drawing by Artheur Girling (1990). Various books continue to be published to the present day which include these types of anaglyph stereo drawings and photographs. The techniques used to create these images came to be known as “Stereo anamorphosis” and the images themselves are now commonly referred to, at least in the US, by the popular term “phantograms.”
People who view phantograms are usually impressed by the ability of such images to create a compelling illusion that a real object is sitting in front of them on top of the image surface or extending forward from a wall mounted display. The commercial possibilities of such an illusion for advertising and display purposes was obvious from the beginning. Macy's patent discloses the use of such images to display pictures of items in a store.
In 1993 Owen Westin created what is believed to by the first photographic phantogram by distorting two images taken with left and right eye cameras situated off angle from their subject. Due in part to Owen Westin's exhibition of his creations at a National Stereographic Society convention, and publication of a phantogram image on the cover of the ISU's summer 1998 issue of Stereoscopic Journal, interest in and experimentation with phantograms blossomed in the 1990s. Many hobbyists experimented with the technique by distorting stereo photographs taken from off axis. Owen Westin obtained U.S. Pat. No. 6,389,286 covering some methods of creating anaglyph phantograms in May of 2002. During the 1990s another photographer, Steve Aubrey, began experimenting with the use of computer based image manipulation programs like Photoshop to perform the distortions necessary to create phantogram images from photographs taken with two cameras or stereo pairs of computer generated images. Steve Aubrey obtained U.S. Pat. No. 6,614,427 in September of 2003 covering distortion methods for the creation of phantograms from digital images.
Since 2005, Toshiba has exhibited a fly's eye lens based autostereoscopic display with a sufficiently wide viewing angle that displays images that can be viewed by people standing at a countertop or sitting at a table and looking down at a version of the display that lays flat. Due to a limited number of 3D perspective views, objects can only extend a few inches above or below the display surface.
Past efforts at producing phantogram images have almost universally used conventional printed or electronic media that must be viewed with 3D glasses to see the images. Autostereoscopic displays have been used experimentally by Toshiba, DTI and a few others. However, there are certain design improvements that can be made to autostereoscopic displays that will make them more easily viewable, and the images more easily seen, from off axis instead of the usual on axis positions. Other improvements can make them more suitable for use in playing electronic games using phantogram images. Furthermore, autostereoscopic display projection systems can be designed to show very large phantogram images to large groups of people. Previous methods of generating stereoscopic images from image pairs have relied on distorting the images obtained from pairs of real or virtual cameras (the latter used in generating computer drawn images). A method of rendering computer generated images that does not require further distortion of the images, and is compatible with existing rendering software packages would save both rendering time and human effort and thus be of benefit.